imagine the following situation:

you open the door of your balcon when you are having a bbq outside. all the smog is getting into your living room. you decide to stay outside as you have to manage turning the meat. you can't close the door completely as you would do this from within your room and you can't lock yourself out. the wind is blowing and always opens the door. again, again and again. all the smog is getting into your house. this print prevents opening the door (as long as your door opens into the room) as the lock mechanism is strong enough to hold the door when the wind is blowing.